1. Field of the Invention
The present invention relates to a system for detecting generation-stop condition of an alternator.
2. Description of the Related Art
Generally, a voltage regulation system of a vehicle alternator has various warning functions. For example, if the alternator stops generating for some reason while the alternator is rotated by an engine, a battery charge lamp is turned on to warn the driver of the abnormal generation stop condition.
A conventional device for monitoring for generation-stops is shown in JP-A-57-142144 entitled "GENERATION CONTROL DEVICE FOR VEHICLE". In the generation control device, an output voltage is obtained by rectifying and smoothing a phase voltage generated in the stator coil, and it is compared with a reference voltage. If the output voltage is lower than the reference voltage, the charge lamp is turned on. If a generation stop occurs due to a break down of the field coil or the like, the charge lamp is turned on so that the driver can be aware of the generation stop condition.
However, if the rotor of the alternator is provided with permanent magnets disposed between the claw poles as shown in JP-A-5-207716 and JP-A-7-123664, magnetic flux is supplied from the permanent magnets even when the field current is not supplied to the field coil. Accordingly, when the rotation speed of the alternator increases, the output voltage becomes higher than the reference voltage, and the generation stop condition cannot be detected. If the reference voltage is raised higher than the voltage generated without the field current supplied to the field coil to prevent the above problem, it would take a long time for the charge lamp to turn off after the engine starts and the alternator generates output voltage higher than the reference voltage. This may mislead the driver to think that the alternator has stopped generating.